A bearing is a mechanical component that serves to fix a shaft of a machine that rotates to a predetermined position and rotate the shaft while supporting a weight of the shaft and a load applied to the shaft. This bearing is generally divided into a rolling bearing and a sliding bearing according to a contact state with the shaft. Since the sliding bearing therebetween is excellent in a capability to support the load applied to the shaft, it is generally used for various connection parts of a construction machine, and the like.
When the shaft is inserted into the sliding bearing to rotate and shake, lubricating oil is supplied to the shaft or sliding bearing in order to prevent the shaft or sliding bearing from being worn due to interfriction.
However, when the sliding bearing to which the lubricating oil is supplied stops and operates, or when the fluctuating load is received from the outside, an oil film formed on the sliding bearing may be partially broken and since an oil film shortage phenomenon occurs due to exhaustion of the lubricating oil after the sliding bearing operates for a predetermined time, the lubricating oil should be supplied periodically to the sliding bearing.
If the sliding bearing operates with the oil film short, an abrasion rate is increased by friction between the shaft and the sliding bearing and seizure (a friction surface between the shaft and the bearing is heated by heat caused by the friction to melt a part of metal, such that the friction surface becomes rough or is fused on an opposite surface) occurs between the shaft and the sliding bearing by friction heat.
Accordingly, an operation of supplying the lubricating oil to the sliding bearing periodically is very important, but since the lubricating oil supplying operation is inconvenient and the mechanical device cannot be operated while performing the supplying operation, an operational rate of the device is also deteriorated.
As a result, a technology that extends a supplying cycle to supply the lubricating oil to the sliding bearing and prevents the seizure from being generated is being attempted variously as a method for solving the problem. Examples thereof may include Korean Unexamined Application Publication No. 10-2006-0070264 in which the lubricating oil is stored in the shaft and the lubricating oil is supplied directly to the shaft when the lubricating oil stored in the shaft is exhausted and Korean Unexamined Application Publication No. 10-1999-0082076 in which a groove is formed in the bearing and the lubricating oil is stored in the groove.
Herein, Korean Unexamined Application Publication No. 10-1999-0082076 (hereinafter, referred to as the ‘related art’) will be described below with reference to FIG. 1.
In the related art, a lubricant pocket 30 having a depth in the range of 0.03 to 0.3 mm and an area ratio to the depth of 10 to 40 mm is formed on a surface 20 to which a bearing 10 slides and serves to supply the lubricating oil to the surface 20 to which the bearing 10 slides, thereby preventing a partial oil film cut-off phenomenon to the bearing 10.
However, in the bearing 10 disclosed in the related art, a circular pocket 30 is formed to disperse a contact surface, the lubricating oil is stored in the formed pocket 30 to constantly maintain the oil film on the surface 20 to which the bearing 10 slides, but since the shape of the pocket 30 is too small, the pocket 30 cannot sufficiently store the lubricating oil, and as a result, there was a limit in extending the lubricating oil supplying cycle.
Meanwhile, in order to increase the amount of the lubricating oil that circulates between the shaft and the sliding bearing, there may be used a method for storing a large amount of lubricating oil by increasing the size of the groove for storing the lubricating oil in the sliding bearing and increasing the number of the grooves. However, when the size of the groove for storing the lubricating oil is increased or the number thereof is increased, an actual contact area between the shaft and the sliding bearing is decreased and a contact pressure between the shaft and the sliding bearing is increased, and as a result, an adverse effect in that the abrasion rate of the sliding bearing is increased and the seizure is generated by the friction heat is taken.
Accordingly, in order to increase the amount of the lubricating oil stored in the sliding bearing and disperse the contact pressure acting between the shaft and the sliding bearing, diameters of the shaft and the sliding bearings should be increased and lengths of the shaft and the sliding bearing in a shaft direction should be extended. However, when the diameter and length of each of the shaft and the sliding bearing are increased, there is a problem in that a sliding bearing assembly including the shaft and the sliding bearing become bigger on the whole.